[ticket/10155] Update jQuery to 1.8.3

Currently included jQuery is old by now, v1.6.2. We should update to
1.8.3. This allows us to take advantage of the latest form of jQuery
event delegation ($.on). I don't think it wise to update to jQuery
1.9.x yet, as many 3rd party scripts still need to be updated to cope
with its deprecated features ($.browser). Therefor, 1.8.3 is the latest
and most widely compatible stable version right now.

PHPBB3-10155
[ticket/10155] Use new migration file for jQuery config update
[ticket/10155] Use more descriptive title for migration file

PHPBB3-10155
[ticket/10155] Make effectively installed test more specific

PHPBB3-10155
[ticket/11495] Add basic interface with nestedset operations

PHPBB3-11495
[ticket/11495] Add abstract implementation of the interface

PHPBB3-11495
[ticket/11495] Add forum implementation of nestedset

PHPBB3-11495
[ticket/11495] Add unit tests for the implemented functions

PHPBB3-11495
[ticket/11495] Use unique properties for the column names

PHPBB3-11495
[ticket/11495] Fix description of get_sql_where

PHPBB3-11495
[ticket/11495] Use array directly instead of phpbb_nestedset_item_interface

PHPBB3-11495
[ticket/11495] Remove item classes

PHPBB3-11495
[ticket/11495] Remove item class from unit tests

PHPBB3-11495
[ticket/11495] Fix column variable names

PHPBB3-11495
[ticket/11495] Move nestedset default values to new method

PHPBB3-11495
[ticket/11495] Manually specify the table columns

PHPBB3-11495
[ticket/11495] Remove item class as its no longer required

PHPBB3-11495
[ticket/11495] Acquire locks for operations that manipulate the tree

PHPBB3-11495
[ticket/11495] Remove acquire locks from forum implementation

PHPBB3-11495
[ticket/11495] Fix Spacing and lowercase on docs

PHPBB3-11495